1. Field of the Invention
The present invention relates to a storage system that constitutes a computer system, and in particular, to a remote copy function and a WORM function that the storage system has.
2. Description of the Related Art
The remote copy is a technique for mirroring data among plural storage systems (here, the storage system includes a storage that records data and a control apparatus that controls the storage; this applies in the following description) without the intervention of a host computer. The remote copy will be explained with a case in which a storage system A having a logical volume A(1) and a storage system B having a logical volume B(1) are connected by a network such as a Fibre Channel or an IP or a private line as an example.
By performing the remote copy, contents recorded in the logical volume A(1) and the logical volume B(1) are kept identical. A host computer is connected to the storage system A, refers to or updates data recorded in the logical volume A(1), and sets the logical volume A(1) and the logical volume B(1) as a pair for the remote copy. When the host computer issues a command for updating the data recorded in the logical volume A(1) to the storage system A, the storage system A updates the data recorded in the logical volume A(1) and sends the updated data to the storage system B. The storage system B updates data recorded in the logical volume B(1). In this way, the data recorded in the logical volume A(1) and the data recorded in the logical volume B(1) are kept identical.
The plural storage systems are arranged remote from each other to perform the remote copy, whereby, when a disaster occurs, an operation of the computer system is continued and restored promptly. Moreover, by performing the remote copy, an operation of data recorded in a certain storage system can be transferred to another storage system. As a method of transferring an operation of data recorded in a certain storage system to another storage system, there are a method of stopping a storage system at time decided in advance to transfer an operation of data to another storage system and a method of transferring an operation of data to another storage system without stopping a storage system. Details of the remote copy are disclosed in U.S. Pat. No. 5,742,792.
WORM is the abbreviation of Write Once Read Many, which means a characteristic of data, that is, data which is recorded once, cannot be updated and can only be referred to. Data having the nature of WORM is effective for proving that the data has not been falsified after the data was recorded and preventing deletion of data due to an operation mistake. The data having the nature of WORM will be hereinafter referred to as WORM data. As a method of realizing the WORM data, there are a method of using a recording device having the nature of WORM as a physical nature like a Write Once CD and a method of adding a device or a program for prohibiting update of data to a storage incorporating a magnetic disk or the like that can be updated many times physically. The latter is disclosed in “Hitachi LDEV Guard”.